Copper Oxide Substrate Research Articles

Superwetting antibacterial copper oxide nanoflake foil substrates generated by thermal oxidation

A facile one-step method of roughened copper foils of 0.0076 ​mm thickness heated on the open flame for 15 ​s produced superhydrophilic surfaces that exhibited superwetting at average radial growths of 10.8 ​mm/s following drop dispensation. Superhydrophilicity was found to deteriorate over time and XRD analysis ruled out compositional change as the cause of this behaviour. Instead, SEM imaging revealed wrinkled 20–30 ​nm-thick nanoflakes that were predominantly stretched out initially to engender superwetting properties via Wenzel wetting. These extended microstructures folded up with time due to relaxation of the residual stresses from the thermal oxidation process, resulting in temporal reduction in superhydrophilicity, which can be restored by reapplying thermal oxidation. The impingement of air with 80 psi pressure on the substrate also caused similar deterioration. The superwetting characteristic also endowed these substrates with anti-bacterial properties where a 56% reduction in bacteria count with Staphylococcus epidermidis was found. • Copper oxide substrates was created by facile one-step thermal oxidation of 0.0076 ​mm thick copper foils in 15 ​s. • The substrate has zero contact angle and spreads at average radial growths of 10.8 ​mm/s following drop dispensation. • Superwetting was promoted by wrinkled 20–30 ​nm-thick nanoflakes that were predominantly stretched out. • Superhydrophilicity deterioration over time in room conditions could be restored by reheating the substrate. • A 56% reduction in Staphylococcus epidermidis count was found due to superwetting and anti-bacterial characteristics.

Epitaxial Growth of Flat, Metallic Monolayer Phosphorene on Metal Oxide.

In recent years, two-dimensional (2D) group VA elemental materials have attracted considerable interest from physics/chemistry and materials science communities, with particular attention paid to honeycomb blue phosphorene. To date, phosphorene is limited to its α-phase and small sizes because it can only be produced by exfoliating black phosphorus crystals. Here, we report the direct synthesis of high-quality phosphorene on a nonmetallic copper oxide substrate by molecular beam epitaxy. By combining scanning tunneling microscopy/spectroscopy, X-ray photoelectron spectroscopy, and first-principles calculations, we demonstrate the growth intermediates and electronic structures of phosphorene on Cu3O2/Cu(111). Surprisingly, the grown phosphorene has a flat honeycomb lattice, similar to graphene, which exhibits a metallic nature. We reveal that the growth mechanism and morphology of phosphorene are strongly correlated with the surface structures of prepared copper oxide, and the resulting phosphorene can be stabilized after high-temperature annealing above 600 K even in oxygen gas. The high stability is closely related to the irregular Moiré pattern and structural corrugations of phosphorene on Cu3O2/Cu(111) that efficiently relieve the surface strain. These results shed light on future fabrication of large-scale, versatile 2D structures for interconnect and device integration.

Morphology and chemical behavior of model CsOx/Cu2O/Cu(111) nanocatalysts for methanol synthesis: Reaction with CO2 and H2.

Cs is a promoter of Cu-based catalysts for the synthesis of alcohols from CO2 hydrogenation. Scanning tunneling microscopy and ambient-pressure x-ray photoelectron spectroscopy were used to study the morphology and chemical properties of surfaces generated by the deposition of cesium on Cu2O/Cu(111) and Cu(111) substrates. CsOx nanostructures were formed after Cs metal was deposited on Cu2O/Cu(111) at 300 K. The formed CsOx protrude over the surface of copper oxide by 2-4 Å, with the dimension at the base of the nanostructures being in the range of 1-3 nm. Heating to elevated temperature induced significant changes in the size and dispersion of the CsOx nanostructures, and there was a clear reconstruction of the copper oxide substrate, which then exhibited long range order with a hexagonally packed structure. The as-deposited and annealed surfaces of CsOx/Cu2O/Cu(111) were more reactive toward CO2 than plain Cu2O/Cu(111) or clean Cu(111). However, none of them were stable in the presence of H2, which fully reduced the copper oxide at 400-450 K. In CsOx/Cu(111), the CsOx nanoclusters were dispersed all over the metallic copper in no particular order. The CsOx species had an average width of 2 nm and ∼1 Å height. The CsOx/Cu(111) systems exhibited the highest activity for the binding and dissociation of CO2, suggesting that the CsOx-copper interface plays a key role in alcohol synthesis.

Large-Scale Synthesis of Strain-Tunable Semiconducting Antimonene on Copper Oxide.

Controlled synthesis of 2D structures on nonmetallic substrate is challenging, yet an attractive approach for the integration of 2D systems into current semiconductor technologies. Herein, the direct synthesis of high-quality 2D antimony, or antimonene, on dielectric copper oxide substrate by molecular beam epitaxy is reported. Delicate scanning tunneling microscopy imaging on the evolution intermediates reveals a segregation growth process on Cu3 O2 /Cu(111), from ordered dimer chains to packed dot arrays, and finally to monolayer antimonene. First-principles calculations demonstrate the strain-modulated band structures in antimonene, which interacts weakly with the oxide surface so that its semiconducting nature is preserved, in perfect agreement with spectroscopic measurements. This work paves the way for large-scale growth and processing of antimonene for practical implementation.

Preconcentration and SERS-based determination of infliximab in blood by usinga TNF-α-modified gold-coated copper oxide nanomaterial.

Infliximab (INF) is a chimeric monoclonal immunoglobulin acting against tumor necrosis factor-alpha (TNF-α). The drug is used for the treatment of chronic autoimmune and inflammatory diseases. A target-specific nanomaterial is presented for the extraction of INF from human plasma along with a label-free surface enhanced Raman spectroscopy (SERS) method for its determination using a handheld device. A gold-coated copper oxide chip was functionalized with TNF-α and used to extract the drug from plasma. INF was recovered from the extractor by lowering the pH value to 2.5. The disulfide bond structure of the drug was then reduced and used for its oriented chemisorption onto a gold-coated copper oxide substrate for SERS measurements using the INF-specific band at 936cm-1. The working range of the SERS method was between 10-7 and 10-14M of reduced INF. The relative standard deviation (RSD), between three different measurements was 4.2% (intra-day) and 7.1% (inter-day). The quantification and detection limits of the assay (LOQ, LOD) were 0.01 pM and 1.4 fM respectively. The SERS detection was cross-validated against ELISA where 99% agreement was found between the two methods. Graphical abstractSchematic representation of the determination of Infliximab (INF) in blood. A gold coated copper oxide chip was functionalised with tumor necrosis factor (TNF-α) and used to extract INF from blood plasma. The captured INF was released, reduced, chemisorbed onto a second gold-coated copper oxide substrate and screened by surface-enhanced Raman spectroscopy (SERS) using a handheld device.

Utilizing the thiol chemistry of biomolecules for the rapid determination of anti-TNF-α drug in blood

The detection of anti-TNF-α drugs require rapid, selective and sensitive biosensors that can be easily utilised at the point of care. Herein, we demonstrate a new biosensing approach that employs target-specific nanomaterial and label free surface-enhanced Raman spectroscopy (SERS) for the selective extraction and rapid determination of Adalimumab (ADB) in human blood plasma. The new method utilises the tumour necrosis factor (TNF-α) for the fabrication of a target-specific nanomaterial for extraction of ADB. The method also uses the thiol chemistry of the purified antibody drug for its chemisorption onto a gold-coated copper oxide substrate. A handheld Raman spectrophotometer is used for the determination of ADB by label free SERS. The limits of quantification (LOQ) and detection (LOD) of the purified and reduced drug by SERS were 0.10 fM and 0.03 fM respectively. ELISA was used for the cross validation of the SERS quantification of ADB where a 98.8% agreement was found between the two methods. Many proteins have disulfide bonds in their molecular structure. Therefore, the demonstrated biosensing approach can be extended for the rapid screening of other proteins and antibody drugs by developing target-specific extractor nanomaterial and utilizing the disulfide bond structure of the purified biomolecules for their label free SERS detection.

Toward Label-Free SERS Detection of Proteins through Their Disulfide Bond Structure.

The molecular structure of many proteins contains disulfide bonds between their cysteine residues. In this work we demonstrate the utilization of the disulfide bond structure of proteins for their label-free determination by surface-enhanced Raman spectroscopy (SERS). The new approach for label-free SERS detection of proteins is demonstrated for human insulin. The protein was selectively extracted from spiked plasma samples using target-specific functionalized nanomaterial. Enzyme-linked immune assay (ELISA) was used to detect insulin in the blood plasma and cross-validate the SERS method. The disulfide bonds in the molecular structure of the protein were chemically reduced and used for their chemisorption onto the gold-coated copper oxide substrate in a unified orientation at a very short distance from the hotspots. The oriented chemisorption of the protein caused significant enhancement to the signal intensity of its Raman vibration modes. This is attributed to the strong short-range electromagnetic and chemical enhancement effects that are experienced by the immobilized protein. Using this approach, label-free and reproducible SERS detection of insulin, down to 10 zM (relative standard deviation [RSD] = 5.52%), was achieved. Sixty-five percent of proteins contain disulfide bonds in their molecular structure. Therefore, the new label-free SERS detection method has strong potential for the determination of ultralow concentrations of proteins at pathology labs and in biology research.

Influence of copper oxide grown on various conducting substrates towards improved performance for photoelectrocatalytic bacterial inactivation

This paper analyzes the role of the conducting layer substrates (Cu and fluorine-doped tin oxide (FTO)) on grown copper oxide (CuO) in order to improve the performance of catalytic bacterial inactivation. Growth of CuO onto Cu substrate was via thermal oxidation of Cu whereas hydrothermal method was employed for CuO growth onto FTO. The surface morphology of CuO varied with respect to the substrates choice and epitaxy, developing particulated thin film and thin film consisting vertically aligned nanorods on Cu and FTO, respectively. Photo- and electro- based reactions were carried out to understand the effect of light, bias, bias-catalyst and light-bias-catalyst combinations, respectively, for the fast killing of E. coli. The experimental results showed a striking improvement in photoelectrocatalytic inactivation of E. coli using plain fabricated copper oxide substrate. The choice of conducting substrate material plays a crucial role in terms of both morphology controlled CuO growth under different facile methods and also governs the electron transfer efficiency to achieve an improved catalytic efficiency. The reaction mechanism was discussed by deriving an appropriate detailed model which is able to predict the experimental data in all the cases. This study gives an insight on energy saving and less carbon footprint approach for bacterial killing in a short interval.

Enhancement of spectral absorption of solar thermal collectors by bulk graphene addition via high-pressure graphite blasting

This work presents the results of construction and testing of a flat plate thermal solar collector with an absorber section that has enhanced radiative properties through the modification of its surface properties. A copper oxide layer is grown on top of the copper absorber by chemically treating it in an ammonia atmosphere. Then, a novel graphene mechanical deposition technique is employed that uses compressed air to deposit few layer graphene on top of the copper oxide substrate. In total, three absorbers are made, one features the copper oxide layer, the second has graphene on top of copper oxide and the third is the reference absorber covered with a black matt paint. The radiative properties of the absorbers are assessed, as well as their thermal efficiencies. The best performance was recorded for the graphene-clad copper oxide collector, with a maximum efficiency of 69.4% compared with an efficiency of around 39.5% for the reference collector.

In situ investigation of M/CuO interface (M is Ti, V, Cr or Mn) by X-ray photoelectron spectroscopy

The technique of X-ray photoelectron spectroscopy has been used to investigate the chemical reactivity at the metal/ CuO interfaces. Thin films of the metallic overlayer (0.5 nm, 1.0 nm and 2.0 nm thickness) were deposited on copper oxide substrates at room temperature. In situ characterization of the interfaces has been performed. The 2p core level regions of the metals have been investigated. The spectral features show considerable reactivity at the interfaces. The core level peaks of the metal are observed to be shifted to the high BE energy side with the appearance of satellites. The spectral data confirm the formation of the metallic oxide at the interface. The satellite structure in the copper region is observed to disappear and the spectral features are found to approach those of elemental copper. The room temperature deposition of the metal on copper oxide therefore results in the reduction of copper oxide to elemental copper followed by the oxidation of the metal. The interface is found to consist of a mixture of metal oxide and elemental copper. The 2.0 nm samples were annealed. These samples show the diffusion of copper oxide through the overlayer. The metal reacts with this diffusing oxide to form metallic oxide. The interface is found to consist of a mixture of unreacted metal, the metal oxide, and elemental copper. The amount of the unreacted metal varied between 0% and 40% and can be controlled by the processing conditions. The investigation shows room temperature chemical reactivity at the metal/ CuO interface and provides a new method of preparing sub-nano-oxide films.

Chemical reactivity at Fe/CuO interface studied in situ by X-ray photoelectron spectroscopy

The technique of X-ray photoelectron spectroscopy has been used to investigate the chemical reactivity at the Fe/CuO interfaces. The 2p core level regions of the metals have been studied. Thin films of iron (thicknesses ranging from 0.3 nm to 2.0 nm) were deposited on copper oxide substrates at room temperature. Earlier investigation on a 0.5 nm overlayer of iron on CuO showed considerable reactivity at the interfaces. The core level peaks of iron are observed to be shifted to the high BE energy side with the appearance of satellites. The spectral data have been compared with those of the oxidized iron and confirms the formation of the iron oxide at the interface. The satellite structure in the copper region is observed to disappear and the spectral features are found to approach those of elemental copper. The interface is found to consist of a mixture of iron oxide and elemental copper. Presence of unreacted iron near the interface has been observed for thicknesses greater than 0.7 nm of the iron overlayer. The effect of temperature on the interface has also been studied. The interface was formed by depositing 2.0 nm of iron on the copper oxide substrate under two different conditions. In one, the substrate temperature was kept constant during the deposition of the iron overlayer. In the other, post deposition annealing of the interface was performed. The iron overlayer is observed to be completely oxidized at the sample temperature of 450 °C and the oxidation is independent of the processing conditions. The amounts of elemental iron and iron oxide in the samples have been estimated by modeling the spectrum using the spectra of elemental iron and pure iron oxide. The process of annealing seems to have more effect on the oxidation of iron than the substrate temperature. The investigation shows room temperature chemical reactivity at the Fe/CuO interface and provides a new method of preparing sub-nano-oxide films of iron.

Grafting and characterization of dodecylphosphonic acid on copper: Macro-tribological behavior and surface properties

Thin film of n-dodecylphosphonic acid (DDPA) was prepared on a copper oxide substrate via a molecular self-assembly process. The composition, structure, organization, surface energy, morphology, and electrochemical behavior of the DDPA film were characterized by means of X-ray photoelectron spectroscopic analysis (XPS), polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), contact angle measurement (CAM), microscopic observations, and electrochemistry. The friction behavior of the DDPA film adsorbed on copper oxide substrate sliding against a Si3N4 ball was examined on a linear reciprocating tribological tester. Worn surfaces of the DDPA film were observed with a scanning electron microscope. All properties of the DDPA film were compared and discussed in terms of sonication effects just after surface functionalization. The presence and organization of alkyl phosphonate molecule on Cu were confirmed by XPS, PM-IRRAS and CAM analyses. PM-IRRAS data gave some indication of tridentate bonding between phosphonic groups and oxidized Cu surface. Electrochemical studies showed strong anti-corrosion behavior. Excellent tribological behavior was observed for DDPA film before sonication (DDPA/Cu BS) under contact pressure of 133MPa and low sliding speed of 1mm·s−1 conditions. In the case of DDPA/Cu BS surface, very low friction coefficient value (μ≈0.12) and increase in antiwear life (100 times higher) were observed, compared to a DDPA film after sonication (DDPA/Cu AS) and a bare Cu substrate.

Effects of moisture and temperature ageing on reliability of interfacial adhesion with black copper oxide substrate

The reliability of adhesion performance of bare Cu, as-deposited and surface-hardened black oxide coatings on Cu substrates was studied. The interfacial adhesion with a polyimide adhesive tape and an epoxy moulding compound was measured using the button shear and tape peel tests after hygrothermal ageing in an autoclave, high temperature ageing and thermal cycles. Moisture adsorption and desorption studies at different aging times suggested that the black oxide coating was effective in reducing the moisture adsorption. The bond strengths for all substrates remained almost unchanged after thermal ageing at 150°C for 8 h. Thermal cycling between −50°C and 150°C for 500 cycles reduced by about 20% the button shear strength of the as-deposited black oxide substrate, but it did change much the bonding performance of the bare Cu substrate. Hygrothermal ageing at 121°C/100% RH in an autoclave was most detrimental to adhesion performance because of the combined effect of elevated temperature and high humidity. The reduction in button shear strength after the initial ageing for 48 h was 50–67%, depending on the type of coating. In all accelerated ageing tests, the residual interfacial bond strengths were consistently much higher for the black-oxide-coated substrates than the bare Cu surface, confirming a higher reliability of black oxide coating. Fracture surfaces analysis of tape-peeled bare copper substrates after 500 cycles of thermal loading revealed a transition in failure mechanism from interfacial to cohesive failure. In contrast, the failure mechanism remained unchanged for black-oxide-coated substrates. The observations made from the button shear and tape peel tests were generally different because of the different fracture modes involved.

Surface characterization and adhesion of black-oxide-coated copper substrate: effect of surface hardening processes

The effects of surface-hardening processes on the changes in surface characteristics and adhesion of black copper oxide substrate with epoxy resins are studied. Various techniques, namely SEM, XPS, AFM, XRD, Auger electron spectroscopy, contact angle goniometry, D-SIMS and RBS, were used to identify the changes in surface characteristics. Dense, fibrillar cupric oxide crystals characterized the as-deposited oxide coating with high surface roughness. The surface-hardening process flattened and consolidated the fibrils without changing the compositional and thermodynamic characteristics of the coated surface. The surface-hardening process reduced the total thickness of copper oxide by approximately 50–150 nm. The reduction in oxide thickness was not a predominant factor for the reduced bond strength of the surface-hardened coating. The bond strengths of both the as-deposited and surface-hardened black oxide coatings increased with oxidation time, until saturation at about 120–150 s. For the as-deposited oxide coating, mechanical interlocking, high wettability and resistance to surface contamination are the three major sources for improved adhesion, amongst which the enhanced mechanical interlocking provided by the fibrillar cupric oxide is the most important. Surface hardening reduced the efficiency of mechanical interlocking mechanism. There was close functional dependence between the button-shear strength and surface characteristics, such as surface roughness, coating thickness and surface free energy.

Raman Spectroscopy Measurements of Interface Effects in C60/Copper-Oxide/Copper

ABSTRACTWe have investigated interface effects in C60/Cu-oxide/Cu structures. C60 thin films were grown under high vacuum by thermal evaporation and the well-known “pentagonal pinch mode” of C60, Ag(2) band was examined by Raman spectroscopy. We observe Raman-active bands centered at 1420, 1448, 1455, and 1465 cm−1 in C60/Cu-oxide/Cu samples with a thin (∼40 nm) C60 overlayer. The 1420, 1448, and 1455 cm−1 Raman bands are not observed in the spectra of pristine C60 powder, copper-oxide substrate, and C60/Cu-oxide/Cu samples with thick (∼1.3 μm) C60 overlayer. We associate these new Raman-active bands with C60/copper-oxide interface.

Surface chemical aspects of polymer/metal adhesion

This paper reports on a three-part study: (1) to determine the effect of surface pretreatment of BDS, a siloxane/polyimide copolymer, on adhesion; (2) to determine the extent of segregation of components of BDS against metal substrates; and (3) to determine the properties of ultrathin polymer films against metal substrates. Surface pretreatment of bds films with aqueous NaOH etched away the top siloxane layer, roughening the polymer surface and producing surface functional groups. These changes resulted in increased wettability and peel strength. Siloxane segregation when bds films were formed against metal surfaces was in the order: Al > Ti > Zn. The relative acidity of the metal oxides as measured by polyvinyl chloride adsorption was in the same order. Reflection-absorption measurements using Fourier transform infra-red spectroscopy were found to be useful in studying the crystallinity of thin polyphenylene sulphide ( pps) films. X-ray photoelectron spectroscopy was used to show that failure occurred through a thin layer of residual pps polymer close to the copper oxide substrate.